Question

Which of the following statements about RuBisCO is true?

Options

• It is active only in the dark.

• It has higher affinity for oxygen than carbon dioxide.

• It is an enzyme involved in the photolysis of water.

• It catalyses the carboxylation of RuBP.

Answer 1

It catalyses the carboxylation of RuBP.

Explanation:

One important enzyme in the Calvin cycle of photosynthesis is RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase). Adding CO₂ catalyses the carboxylation of RuBP (ribulose-1,5-bisphosphate), producing two molecules of 3-phosphoglycerate. RuBisCO does not function in the absence of light. RuBisCO has a greater affinity for CO₂ than for O₂, but it can also catalyse oxygenation (photorespiration) under certain conditions (such as high O₂ concentrations). It is not involved in the photolysis of water, which is carried out by photosystem II as part of the light-dependent processes.